气泡幕对异齿裂腹鱼的阻拦效果

为了研究气泡幕对异齿裂腹鱼的阻拦效果,在环形水槽装置中分别设置60、90、120 L·min~(-1) 3种不同气量的气泡幕,在静水条件下,比较不同时间段气泡幕对异齿裂腹鱼的阻拦效果和异齿裂腹鱼空间分布的变化。结果表明:3种气量的气泡幕对异齿裂腹鱼都有明显的阻拦效果,且阻拦率无显著差异(P=0.130),在气量为60 L·min~(-1)时阻拦率最高,为81.3%;实验过程中鱼对气泡幕无明显的适应性; 90和120 L·min~(-1)两种气量下,异齿裂腹鱼喜欢在气泡幕附近停留。本研究结果可为气泡幕诱驱鱼技术在工程上的应用提供参考。     

齐口裂腹鱼在低照度下的趋光行为

以野生亚成体齐口裂腹鱼为实验对象,进行了光色选择实验和趋光性实验,旨在找到异齿裂腹鱼的偏好光色和光强。实验变量设置5种光色(红、黄、蓝、绿和黑暗)及3种流速工况(0、0.15和0.30 m·s-1)。在光色选择实验中,研究了齐口裂腹鱼在静水、光强照度为10 lx下不同光环境下的偏好行为。结果表明:齐口裂腹鱼对5种光色的喜好顺序为绿色蓝色黑色红色黄色,且在绿光和蓝光区域中的分布率和选择指数显著大于红光和黄光区域(P0.05)。在趋光性实验中,研究了光源光照强度均为20 lx,不同水流流速(0、0.15和0.30 m·s-1)时齐口裂腹鱼的趋光性,发现:无论在静水还是动水工况下,齐口裂腹鱼均对蓝光和绿光表现为正趋光性,对红光和黄光表现为负趋光性;齐口裂腹鱼属弱趋光性鱼类,且其趋光性不随水流的增大而增大,趋光阈值为1.40~2.65 lx。依据实验结果,我们建议在工程中采用光强照度为20 lx的绿光进行诱集齐口裂腹鱼。     

MS-222对两种规格的异齿裂腹鱼麻醉效果研究

通过MS-222对2种规格的异齿裂腹鱼进行麻醉行为特征研究, 为高原鱼类的麻醉以及运输提供技术支持。试验表明: MS-222麻醉大规格(25.0±1.5) cm和小规格(14.8±2.3) cm异齿裂腹鱼时, 在麻醉时期3期以内, 呼吸频率增加并之间无显著性差异, 在麻醉4期以后呼吸频率才开始显著下降。MS-222麻醉大规格和小规格异齿裂腹鱼的有效质量浓度分别为150—180 mg/L和150 mg/L。在此浓度范围内, 大规格异齿裂腹鱼在MS-222麻醉液中, 5min之内达到4级麻醉状态, 5min之内苏醒恢复, 且在麻醉液中浸浴20min后成活率为100%时的浓度; 小规格异齿裂腹鱼在MS-222麻醉液中, 5min之内达到4级麻醉状态, 7min之内苏醒恢复, 且在麻醉液中浸浴20min后成活率为100%时的浓度。大规格异齿裂腹鱼在180 mg/L的MS-222溶液中麻醉5min, 在空气中进行暴露0—15min, 复苏时间无显著性差异(P>0.05); 小规格异齿裂腹鱼在150 mg/L的MS-222溶液中麻醉5min, 在空气中进行暴露0—15min, 复苏时间存在显著性差异(P<0.05)。     

MS-222对两种规格的异齿裂腹鱼麻醉效果研究（英文）

通过MS-222对2种规格的异齿裂腹鱼进行麻醉行为特征研究,为高原鱼类的麻醉以及运输提供技术支持。试验表明:MS-222麻醉大规格(25.0±1.5) cm和小规格(14.8±2.3) cm异齿裂腹鱼时,在麻醉时期3期以内,呼吸频率增加并之间无显著性差异,在麻醉4期以后呼吸频率才开始显著下降。MS-222麻醉大规格和小规格异齿裂腹鱼的有效质量浓度分别为150—180 mg/L和150 mg/L。在此浓度范围内,大规格异齿裂腹鱼在MS-222麻醉液中, 5min之内达到4级麻醉状态, 5min之内苏醒恢复,且在麻醉液中浸浴20min后成活率为100%时的浓度;小规格异齿裂腹鱼在MS-222麻醉液中, 5min之内达到4级麻醉状态, 7min之内苏醒恢复,且在麻醉液中浸浴20min后成活率为100%时的浓度。大规格异齿裂腹鱼在180 mg/L的MS-222溶液中麻醉5min,在空气中进行暴露0—15min,复苏时间无显著性差异(P0.05);小规格异齿裂腹鱼在150 mg/L的MS-222溶液中麻醉5min,在空气中进行暴露0—15min,复苏时间存在显著性差异(P0.05)。     

异齿裂腹鱼幼鱼模拟麻醉运输研究

异齿裂腹鱼(Schizothorax o'connori)是分布于雅鲁藏布江中游的高原特有鱼类。受人类活动影响,异齿裂腹鱼自然种群资源迅速下降。作为鱼类保护研究与实践的重要支撑技术之一,鱼类麻醉运输技术在高原鱼类中的运用还没有公开报道。本研究观察了8种MS-222浓度(0、10、20、30、40、50、60、70 mg/L)模拟麻醉运输条件下,异齿裂腹鱼幼鱼(全长17～25cm)的行为表现及运输水质的变化。结果显示,在0～4 h内,各处理组的水体溶解氧和总氮含量大都呈上升趋势,pH呈下降趋势,4～12 h期间各处理组的溶解氧、pH和总氮无统一的变化趋势。MS-222浓度为0～30 mg/L时,试验鱼均未进入麻醉状态;MS-222浓度为40～50 mg/L时,试验鱼在0～8 h内保持深度麻醉或轻度麻醉状态,8～12 h麻醉剂逐渐失效,试验鱼可慢慢恢复正常活动,12 h内没有出现死亡情况;MS-222浓度为60～70 mg/L时,试验鱼进入过度麻醉状态,并出现了死亡。本研究表明,适宜异齿裂腹鱼的MS-222浓度为40～50 mg/L,麻醉运输的时间应控制在8h内。     

齐口裂腹鱼上溯过程中“冲刺-滑行”行为对水动力的响应

研究以西南山区特有鱼种齐口裂腹鱼(Schizothorax prenanti)为研究对象, 对其游泳行为模式进行量化解译, 寻找其偏好的水动力学条件, 构建水流条件与生态行为的纽带。运用具有流速梯度的水槽创造非均匀流场条件, 得到齐口裂腹鱼在室内试验水槽内上溯的视频图像。运用图像识别技术, 计算上溯全过程的游泳动力学指标摆尾角度与摆尾频率, 在此基础上实现生态学与水动力学的耦合研究。研究表明, 齐口裂腹鱼在上溯过程中喜好在具有流速梯度处通过改变摆尾角度和摆尾频率等来适应非均匀流场, 其喜好摆尾角度为25°—35°, 喜好摆尾频率为2.5—3.5次/s, 偏好流速为0.20—0.40 m/s。随着水流速度的增大, 摆尾角度呈现逐渐减小的趋势, 且齐口裂腹鱼偏好选择在流速由大变小的区域, 进行摆尾冲刺加速, 且更趋向于摆尾角度变化为“弱强弱”的摆尾模式。滑行阶段引入滑行流速系数, 量化表示摆尾角度、滑行距离和流速三者间的耦合关系, 通过计算滑行距离对水流负方向上位移的贡献率, 得到滑行方向与水流负方向夹角。研究表明, 滑行流速系数为1.0—3.0时具有代表性, 齐口裂腹鱼对滑行方向与水流负方向夹角的偏好为40°—60°。研究利用多指标量化评价的方法, 以复杂流场为背景条件, 进一步满足过鱼设施建设需求。     

雅鲁藏布江中游裂腹鱼类的分布及栖息地特征

分别于2015年4月和10月对雅鲁藏布江中游裂腹鱼类的分布与栖息地环境特征进行了调查。结果表明:雅鲁藏布江中游现分布有裂腹鱼类6种,即异齿裂腹鱼(Schizothorax oconnori)、双须叶须鱼(Ptychobarbus dipogon)、拉萨裸裂尻鱼(Schizothorax younghusbandi)、拉萨裂腹鱼(Schizothorax waltoni)、巨须裂腹鱼(Schizothorax macropogon)和尖裸鲤(Oxygymnocypris stewarti);尖裸鲤仅在雅鲁藏布江仁布以上江段出现,异齿裂腹鱼和拉萨裸裂尻鱼在所有调查断面均有分布。RDA分析显示,河宽、流速和pH是影响裂腹鱼类栖息地选择的主要因子。针对当前雅鲁藏布江中游存在的过度捕捞、外来物种入侵和梯级水电开发等问题,建议管理部门采取划定保护区、禁捕、宣传放生土著鱼类等措施来维持裂腹鱼类栖息地的有效性。     

基于雅砻江两种裂腹鱼游泳能力的鱼道设计

为探究雅砻江两种裂腹鱼的游泳能力,给过鱼设施设计和鱼类游泳行为学研究提供基础参数,本研究采用递增流速法对长丝裂腹鱼、齐口裂腹鱼的感应流速、临界游泳速度、突进游泳速度进行测试,采用固定流速法对长丝裂腹鱼的耐久游泳速度进行测试。结果表明: 长丝裂腹鱼与齐口裂腹鱼的感应流速随着体长的增加均出现了先增加后平稳的趋势,但最大感应流速均小于0.2 m·s^-1;长丝裂腹鱼的临界游泳速度与突进游泳速度分别为(0.81±0.20)和(1.49±0.26) m·s^-1,相对临界游泳速度为(4.90±1.73) BL·s^-1,相对突进游泳速度为(9.77±1.72) BL·s^-1(BL为体长);齐口裂腹鱼的临界游泳速度与突进游泳速度分别为(0.73±0.24)和(1.17±0.39) m·s^-1,相对临界游泳速度为(6.88±2.82) BL·s^-1,相对突进游泳速度为(11.75±2.77) BL·s^-1。耐久测试发现,随着流速增加(0.7～1.5) m·s^-1,长丝裂腹鱼持续游泳时间与水流速度呈负相关,疲劳时间(T)与水流速度(V)的关系可以拟合为lgT=-2.52V+5.59,预测鱼道长度(d)与鱼道内可通过的最大平均水流速度(V_fmax)的关系式为V_{f max}=-0.17lnd+1.74。根据试验结果,当以长丝裂腹鱼和齐口裂腹鱼为主要过鱼对象时,建议鱼道内最小水流速度应大于0.2 m·s^-1,进口及竖缝处水流速度为0.73～1.67 m·s^-1,休息池主流水流速度为0.2～0.7 m·s^-1。     

两种标记方法对异齿裂腹鱼幼鱼的标记效果研究

异齿裂腹鱼（Schizothorax oconnori）是仅分布于雅鲁藏布江中游的高原特有鱼类。本研究在室内水泥池条件下探讨了可见植入荧光（VIE）标记和T型标志牌对异齿裂腹鱼幼鱼的短期（30 d）标记效果。共设置3个处理组,分别为VIE标记组、T型标志牌组和对照组。VIE标记的标记部位为试验鱼的头部表皮,T型牌的标记部位为试验鱼的背鳍基部。试验期间的水温为10.1~11.7 ℃,溶解氧为3.65~7.54 mg/L。结果显示,各标志处理组在试验期间没有显著生长,各组间的全长也没有显著性差异。VIE标记组、T型牌组和对照组的平均存活率分别为95.8%、92.0%和97.5%。VIE标记组和T型牌组的平均标志保持率分别为100%和88.95%。本研究表明,VIE标记是适宜异齿裂腹鱼幼鱼的短期标记方式。     

异齿裂腹鱼仔鱼的黑色素分布

本文运用组织学方法对异齿裂腹鱼仔鱼发育过程中除眼睛以外的黑色素分布进行研究。结果表明: 异齿裂腹鱼孵化出膜后,黑色素在各个组织器官的出现顺序为: 脑颅外膜→围心腔、背部皮肤→腹腔内膜、脊髓腔。其中,出膜5 d时脑颅外膜处出现黑色素;7 d时围心腔和背部皮肤出现黑色素;10 d时腹腔内膜、脊髓腔出现黑色素。异齿裂腹鱼出膜10 d后,其皮肤和内脏器官(脑颅、围心腔、腹腔内膜、脊髓腔)均具有黑色素,且主要分布在背侧。黑色素在异齿裂腹鱼仔鱼发育过程中的出现时序和分布规律可能与其所处的强紫外辐射环境有关。本研究可为研究鱼类黑色素的紫外防护机制提供参考,并为今后高原鱼类仔鱼的培育条件优化提供理论支撑。     

Effects of turbidity on estuarine fish response to strobe lights

The efficacy of a strobe light and a combined strobe light/bubble curtain system was evaluated under turbid water conditions as a fish avoidance scheme. Three estuarine species commonly impinged at electric generating facilities along the Atlantic coast of the United States were tested: Atlantic menhaden (Brevoortia tyrannus), spot (Leiostomus xanthurus), and white perch (Morone americana). The strobe light/bubble curtain combination was the most effective system studied in all cases. An interesting phenomenon was that fish avoidance to strobe light systems increased with turbidity over the range tested (clear, 39–45 and 102–138 NTU).     

Viability and longevity of pollen from transgenic and nontransgenic tall fescue (Festuca arundinacea) (Poaceae) plants

Pollen is an important vector of gene flow in plants, particularly for outcrossing species like tall fescue. Several aspects of pollination biology were investigated using pollen from transgenic and nontransgenic plants of tall fescue (Festuca arundinacea Schreb.), the most important forage species worldwide of the Festuca genus. To effectively assess in vitro pollen viability in tall fescue, an optimized germination medium (0.8 mol/L sucrose, 1.28 mmol/L boric acid and 1.27 mmol/L calcium nitrate) was developed. Treatment with relatively high temperatures (36° and 40°C) and high doses of UV-B irradiation (900-1500 μW/cm(2)) reduced pollen viability, while relative humidity did not significantly influence pollen viability. Viability of pollen from transgenic progenies (T1 and T2) was similar to that from seed-derived control plants. Pollen from primary transgenics (T0) and primary regenerants (R0) had various levels of viability. Hand pollination using the primary regenerants and transgenics revealed that no seed set could be obtained when pollen viability was lower than 5%. Pollen from transgenic progenies and nontransgenic control plants could survive up to 22 h under controlled conditions in growth chamber. However, under sunny atmospheric conditions, viability of transgenic and nontransgenic pollen reduced to 5% in 30 min, with a complete loss of viability in 90 min. Under cloudy atmospheric conditions, pollen remained viable up to 240 min, with about 5% viability after 150 min. This report is the first on pollen viability and longevity in transgenic forage grasses and could be useful for risk assessment of transgenic plants.     

Rectification of the water permeability in COS-7 cells at 22, 10 and 0°C

The osmotic and permeability parameters of a cell membrane are essential physico-chemical properties of a cell and particularly important with respect to cell volume changes and the regulation thereof. Here, we report the hydraulic conductivity, L(p), the non-osmotic volume, V(b), and the Arrhenius activation energy, E(a), of mammalian COS-7 cells. The ratio of V(b) to the isotonic cell volume, V(c iso), was 0.29. E(a), the activation energy required for the permeation of water through the cell membrane, was 10,700, and 12,000 cal/mol under hyper- and hypotonic conditions, respectively. Average values for L(p) were calculated from swell/shrink curves by using an integrated equation for L(p). The curves represented the volume changes of 358 individually measured cells, placed into solutions of nonpermeating solutes of 157 or 602 mOsm/kg (at 0, 10 or 22°C) and imaged over time. L(p) estimates for all six combinations of osmolality and temperature were calculated, resulting in values of 0.11, 0.21, and 0.10 μm/min/atm for exosmotic flow and 0.79, 1.73 and 1.87 μm/min/atm for endosmotic flow (at 0, 10 and 22°C, respectively). The unexpected finding of several fold higher L(p) values for endosmotic flow indicates highly asymmetric membrane permeability for water in COS-7. This phenomenon is known as rectification and has mainly been reported for plant cell, but only rarely for animal cells. Although the mechanism underlying the strong rectification found in COS-7 cells is yet unknown, it is a phenomenon of biological interest and has important practical consequences, for instance, in the development of optimal cryopreservation.     

A method for detecting the temporal sequence of muscle activation during cycling using MRI

Surface electromyography (EMG) can assess muscle recruitment patterns during cycling, but has limited applicability to studies of deep muscle recruitment and electrically stimulated contractions. We determined whether muscle recruitment timing could be inferred from MRI-measured transverse relaxation time constant (T(2)) changes and a cycle ergometer modified to vary power as a function of pedal angle. Six subjects performed 6 min of single-leg cycling under two conditions (E0°-230° and E90°-230°), which increased the power from 0°-230° and 90-230° of the pedal cycle, respectively. The difference condition produced a virtual power output from 0-180° (V0°-180°). Recruitment was assessed by integrating EMG over the pedal cycle (IEMG) and as the (post-pre) exercise T(2) change (ΔT(2)). For E0°-230°, the mean IEMG for vastus medialis and lateralis (VM/VL; 49.3 ± 3.9 mV·s; mean ± SE) was greater (P < 0.05) than that for E90°-230° (17.9 ± 1.9 mV·s); the corresponding ΔT(2) values were 8.7 ± 1.0 and 1.4 ± 0.5 ms (P < 0.05). For E0°-230° and E90°-230°, the IEMG values for biceps femoris/long head (BF(L)) were 37.7 ± 5.4 and 27.1 ± 5.6 mV·s (P > 0.05); the corresponding ΔT(2) values were 0.9 ± 0.9 and 1.5 ± 0.9 ms (P > 0.05). MRI data indicated activation of the semitendinosus and BF/short head for E0°-230° and E90°-230°. For V0°-180°, ΔT(2) was 7.2 ± 0.9 ms for VM/VL and -0.6 ± 0.6 ms for BF(L); IEMG was 31.5 ± 3.7 mV·s for VM/VL and 10.6 ± 7.0 mV·s for BF(L). MRI and EMG data indicate VM/VL activity from 0 to 180° and selected hamstring activity from 90 to 230°. Combining ΔT(2) measurements with variable loading allows the spatial and temporal patterns of recruitment during cycling to be inferred from MRI data.     

The avoidance strategy of environmental constraints by an aquatic plant Potamogeton alpinus in running waters

Aquatic plants anchored in streams are under pressure from various constraints linked to the water flow and display strategies to prevent their damage or destruction. We assume that the responses of aquatic plants to fast‐water flow are a manifestation of a trade‐off consisting in either maximizing the resistance to damage (tolerance strategy) in minimizing the hydrodynamic forces (avoidance strategy), or both. Our main hypothesis was that Potamogeton alpinus demonstrate the avoidance strategy. We analyzed architecture traits of the modules of this clonal plant from slow‐ and fast‐flowing streams. In fast‐flowing waters, the avoidance strategy of P. alpinus is reflected by the following: (1) the presence of floating leaves that stabilize the vertical position of the stem and protect the inflorescence against immersion; (2) elongation of submerged leaves (weakens the pressure of water); and (3) shoot diameter reduction and increase in shoot density (weakens the pressure of water, increases shoot elasticity), and by contrast in slow‐water flow include the following: (4) the absence of floating leaves in high intensity of light (avoiding unnecessary outlays on a redundant organ); (5) the presence of floating leaves in low intensity of light (avoidance of stress caused by an insufficient assimilation area of submerged leaves).     

Effects of bathing and hot footbath on sleep in winter

The effects of daily bathing and hot footbath (immersion of feet in hot water) in winter on the sleep behavior of nine healthy female volunteers were studied. Subjects were assigned to three sleep conditions: sleep after bathing (Condition B), sleep after hot footbath (Condition F), and sleep without either treatment (Control). Polysomnograms (consisting of electroencephalograph, electrooculograph, and electromyograph) were obtained, and body movements during sleep were measured while monitoring both the rectal and skin temperatures of subjects. In addition, subjective sleep sensations were obtained with a questionnaire answered immediately by the subjects on awakening. The rectal temperature increased by approximately 1.0 degree C under Condition B, but this elevation was not observed under Condition F compared with Control. In contrast, the respective increases in the mean skin temperature of participants subjected to bathing and hot footbath were greater than those of Control, although these temperature differences became negligible 2 h after subjects went to bed. The sleep onset latency was shortened under both conditions compared with Control. Body movements during the first 30 min of sleep in Control were greater than under the other conditions. Rapid eye movement (REM) sleep decreased under Condition B compared with Condition F, and stage 3 was greater under the latter condition compared with Control. As such, the subjective sleep sensations were better under the two treatment conditions. These results suggest that both daily bathing and hot footbath before sleeping facilitates earlier sleep onset. A hot footbath is especially recommendable for the handicapped, elderly, and disabled, who are unable to enjoy regular baths easily and safely.     

Molecular analysis of shower curtain biofilm microbes

Households provide environments that encourage the formation of microbial communities, often as biofilms. Such biofilms constitute potential reservoirs for pathogens, particularly for immune-compromised individuals. One household environment that potentially accumulates microbial biofilms is that provided by vinyl shower curtains. Over time, vinyl shower curtains accumulate films, commonly referred to as "soap scum," which microscopy reveals are constituted of lush microbial biofilms. To determine the kinds of microbes that constitute shower curtain biofilms and thereby to identify potential opportunistic pathogens, we conducted an analysis of rRNA genes obtained by PCR from four vinyl shower curtains from different households. Each of the shower curtain communities was highly complex. No sequence was identical to one in the databases, and no identical sequences were encountered in the different communities. However, the sequences generally represented similar phylogenetic kinds of organisms. Particularly abundant sequences represented members of the alpha-group of proteobacteria, mainly Sphingomonas spp. and Methylobacterium spp. Both of these genera are known to include opportunistic pathogens, and several of the sequences obtained from the environmental DNA samples were closely related to known pathogens. Such organisms have also been linked to biofilm formation associated with water reservoirs and conduits. In addition, the study detected many other kinds of organisms at lower abundances. These results show that shower curtains are a potential source of opportunistic pathogens associated with biofilms. Frequent cleaning or disposal of shower curtains is indicated, particularly in households with immune-compromised individuals.     

Molecular Analysis of Shower Curtain Biofilm Microbes

Households provide environments that encourage the formation of microbial communities, often as biofilms. Such biofilms constitute potential reservoirs for pathogens, particularly for immune-compromised individuals. One household environment that potentially accumulates microbial biofilms is that provided by vinyl shower curtains. Over time, vinyl shower curtains accumulate films, commonly referred to as “soap scum,” which microscopy reveals are constituted of lush microbial biofilms. To determine the kinds of microbes that constitute shower curtain biofilms and thereby to identify potential opportunistic pathogens, we conducted an analysis of rRNA genes obtained by PCR from four vinyl shower curtains from different households. Each of the shower curtain communities was highly complex. No sequence was identical to one in the databases, and no identical sequences were encountered in the different communities. However, the sequences generally represented similar phylogenetic kinds of organisms. Particularly abundant sequences represented members of the α-group of proteobacteria, mainly Sphingomonas spp. and Methylobacterium spp. Both of these genera are known to include opportunistic pathogens, and several of the sequences obtained from the environmental DNA samples were closely related to known pathogens. Such organisms have also been linked to biofilm formation associated with water reservoirs and conduits. In addition, the study detected many other kinds of organisms at lower abundances. These results show that shower curtains are a potential source of opportunistic pathogens associated with biofilms. Frequent cleaning or disposal of shower curtains is indicated, particularly in households with immune-compromised individuals.     

Hemodynamic effects of nicotine in canine skeletal muscle.

Studies were conducted in 36 artificially ventilated, anesthetized dogs to clarify hemodynamic effects of nicotine in resting gracilis muscle. In Series 1, effects of intravenous nicotine (36 micrograms/kg/min) were evaluated in (i) intact muscles (Condition 1), (ii) denervated muscles (Condition 2), (iii) denervated muscles following local alpha-adrenergic blockade (Condition 3), (iv) denervated muscles following combined local alpha- and beta-adrenergic blockade (Condition 4), and (v) intact muscles with aortic pressure maintained constant (Condition 5). In Series 2, nicotine was infused directly into the gracilis artery at a rate of 3.6 micrograms/kg/min. Muscle blood flow was obtained with an electromagnetic flowmeter and used to calculate vascular resistance and oxygen consumption (Fick equation). Plasma catecholamine levels were determined with a radioenzymatic method. Intravenous nicotine doubled mean aortic pressure under Conditions 1-4. In intact and denervated muscles (Conditions 1 and 2) proportional increases in vascular resistance, reflective of vasoconstriction, held blood flow constant. Muscle oxygen consumption was unchanged. alpha-Adrenergic blockade with phenoxybenzamine following denervation (Condition 3) converted muscle vasoconstriction to vasodilation during nicotine infusion. Additional beta-adrenergic blockade (Condition 4) restored muscle vasoconstriction. Nicotine-induced muscle vasoconstriction was maintained under controlled pressure (Condition 5). Intravenous nicotine significantly increased plasma catecholamine levels. Intra-arterial infusions of nicotine (Series 2) caused no hemodynamic changes in muscle. In conclusion, intravenous nicotine caused vasoconstriction in muscle, which was not due to reduced metabolic demand, pressure-flow autoregulation, or a direct [corrected] effect on vascular smooth muscle, but to stimulation of alpha-adrenergic receptors. Following denervation, this vasoconstriction was maintained by elevated plasma catecholamines. alpha-Adrenergic blockade unmasked nicotine-induced vasodilation mediated by beta-adrenergic receptors, whereas combined alpha- and beta-adrenergic blockade unmasked nicotine-induced vasoconstriction by a nonadrenergic mechanism.